Multiple switch-board



(No Model.) 3 Sheets-Sheet l.

MG. KBLLOGG.

MULTIPLE SWITCH BOARD.

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(No Model.) 3 Sheets-Sheet 2. A

M. G. KELLOGG.

MULTIPLE SWITCH BOARD.

Patented Aug. 21, 1888.

Lake tra@ TATES arent @risica lIlLO G. KELLOGG, OF HYDE PARK, ILLINOIS.

ivi ULTiPLE SWITCHmBOARD.

SPECIFCATXON forming part of Letters Patent No. 388,283,dal1ed August 21, 1888.

(No model.)

To @ZZ whom, it may concern:

Be it known that l, Mito G. KnLLoeo, of Hyde Park, Illinois, have discovered certain new and useful Improvements in Multiple Switch-Boards for '.lelephoneExchanges, of which the following is such a full, clear, concise, and exact description as will enable those skilled in the art ot' telephony to practice my invention, reference being had to the accompanying drawings, forming a part of this specitication.

My invention is designed to facilitate the work of switching at the central oftice of a telephone-exchange district system.

It consists, first, of a multiple switch-board system, which I shall hereinafter describe and claim in detail, and it consists, secondly, of a certain central -ot'iice system of cords with plugs, keys, switches, telephone, battery, and circuits for answering, testing, calling, and clearing out subscribers7 lines, which I shall hereinafter describe and claim in detail, said systembeingapplicabietosaidmultipleswitchboard'system mentioned above, and to other systems of telephoneexchange switch-boards.

In my multiple switchboard system I place as many switch-boards in the central office as are found necessary or desirable in order to properly answer the calls and connect and dis connect thc subscribers lines. On each board I place, for-each telephone-line which centers at the oi'tice, a spring-jack or similar switch having two insulated contactpoints and adapted to receive a plug, and when the plug is inserted to disconnect the contact-points and connect one of them with the ilexible conductingcord attached to the plug, and when the plug is withdrawn t0 again connect the contact-points. Gn each board I also place, for each ot' said telephone-lines, a metallic test-bolt or contact-piece insulated from the other parts ofthe apparatus, except as by conducting-wires, as shown and described.

For convenience I hare used the metallic test-bolt or contactrpiece of a line as a frame work to support the parts of the springjack switch of that line, the parts being insulated suitably for the purposes required. The

Switches for a line ou the different boards may be called a series ot'switchcs,77 and the testbolts of aline may be called a series of testbolts. A

Figure 2 ot' the drawings shows an edge View of a spring-jack switch, such as I use in my multiple switch-board system, with part of the metal frame-work broken away so as to show the position ofthe plug when it is inserted into the switch. The iigure shows the plug inserted into the switch.

ce b 0 el', a b c and d in Fig. l are also edge views ofthe springjack switch, c,b,and c having plugs inserted.

The same letters are used to designate the saine parts of the spring-jack switches shown in Figs. l and 2.

7s is the metal frame-work oi' the switch, which I also use as a testbolt.

f is a metal contact-screw passing through the framework, 7c and insulated from it by the insulation e, which also passes through k.

7L is the contact-spring of the switch. It is insulated from thet'ramework 7:,and is in coutact with the point g of t-he screw f when the plug is not inserted in the switch. tI/ hen the plug is inserted,the contact between the point g and the spring z is broken, and the metal part of the plug is in contact with the spring, as shown.

` m m are insulating-pieces which insulate spring 7L from the metal frame-work 7;.

j" is a connecting-piece in electric contact with screwf.

7c is a connecting-piece in electric contact with frame-work 7c.

h is a connecting-piece in electric contact with spring h.

A n extension of r passes througi. insulating-pieces in m, conncctingpieces h k', and contact-spring h, and has a screwthread cnt on its end. n is a nut which iits this thread and holds the parts in place, as shown.

Fig. l of the drawings shows in detail the central-ottico apparatus and connections in my multiple switch-board system. Figs. l, l", l, and I'l show in detail subscribers station apparatus and connections used in the system. Figs. l and lshow modifications ot'subscribers station apparatus and connections. Fig. 2 shows an edge view ol the spring-jack switch used in the system. Fig. 3 represents a cen- 2 asaza trai-office system of crods, plug, and other apparatus for the use of an operator for making and answering connections and testing. Fig. 4 shows parts of two boards for open-circuit lines with their connections.

D in Fig.2 represents aswitch-plug adapted for use with the switch, and with. a portion of its exible cord attached. G is a solid metal cylinder of the plug with a rounded end, as shown. made ofsome insulating material,as hard rubber. E is a metal strip which makes the connection between the cord andthe metal cylinder.

Fig. 1 shows in detail the general arrangement and operation of the central-office appatus of my multiple switch-board system.` A is a broken sectional view of the frame-work of one of the switch-boards required for the central office, and adapted to receive spring-jack switches for all of the lines which center at the office. Four spring-jacks, a, b', c', and d', are shownmounted on this frame-work. A is a broken sectional view of the framework of another of the switch-boards required for the central office, also adapted to receive springjack switches for all ofthe lines which center at the office. Four spring-jack switches, ct", b, c, and d, are also shown mounted on this frame-work, and they are for thesame four lines as are the spring-jacks shown on framework A. I have shown only two boards in operation. If more were required, they would be fitted up similar to those shown, and thel connections between all would be similar to that shown, and such as would be evident to those skilled in the art.

Fig. l also shows parts of the four lines to which belong the spring-jacks shown. They are marked Line No. 1,7 Line No. 2,7 Line No. 3, and Line No. 4.?7 To line No. l belong springjacks a a. To line No. 2 belong spring-jacks b b. To line No. 3 belong spring-jacks c c. To line No. 4 belong springjacks d d.

Figs. la, l, l, and 11 show parts of lines Nos. l, 2, 3, and 4, and also their station outiits, which are marked WV, X, Y, and Z, respectively. I have represented the usual magneto-bell system of calling with closed-circuit lines and calling-annunciators at the central oftice, and I have represented two of the lines (lines No. l and No. 2) as having their annunciators located at switch-board A, their calls Vto be attended toat that board. Their annunciators are marked w and z, respectively. I have represented lines No. 2 and No. 3 as having their annunciators at switch-board A', and they are marked x and i, respectively. I have represented at the subscribers stations the usual forms of telephone apparatus, including battery transmitter, receiving telephone, induction-coil, battery, and telephoneswitch. The magneto-generators of the station outfits are marked l, the bells are marked 2, the battery-transmitters 3, the primaries of the inductioncoils 4, the secondaries of the C' is the handle of the plug, and isI induction-coils 5, the batteries 6, the telephone switches 7, and the receiving-telephones 8. I have represented with these outfits the gravity-switch ordinarily used with the handtelephone. The circuit at each station outt is as shown, the solid lines representing the main line passing through'the generator, bell, transmitter, primary, and secondary of" the induction-coil and hand-telephone to ground, and the broken lines representing the local connections, as shown.

It will be seen that the transmitter and primary of the induction-coil are shunted by a branch or derived circuit, in which is a battery and a pair of contact-points of the telephone-switch, and that these points are open when the telephone is on the switch and closed when it is off the switch.

It is evident from an examination of the circuits that when the hand-telephone is off from its switch the battery is on closed circuit with the transmitter and primary of the inductioncoil, and that as the two latter are also in the main circuit part of the battery-currentwill thengo to line, the proportion going to line `being dependent on the comparative resistance of the derived circuit which contains the transmitter and primary ofthe induction-coil on the one hand, and, on the other hand, that which includes the rest of the main circuit, according to the well-known law ofthe distribution ot' current in derived circuits. It is evident from the circuits that when a telephone is on its switch the battery is open and no current from it goes to line. therefore acts as a transmitter-battery for the suhscribers station outlit, and by sending current to line where it is switched for use with the transmitter, and by sending it only then the same battery also operates as a testbattery, in a manner which will hereinafter be described. The telephone of station Z is shown as on its switch. The telephones of W, X, and Y are shown as not on their switches.

The connections of the lines through their spring-jacks on the different boards and to their test-bolts and through their calling-annunciators to ground are shown in Fig. 1. The mainline circuits may be traced as follows: The circuit of line No. 4, for instance, beginning at the ground in the central office, passes through its annunciator z and thence through wire 61" and connecting-piece f of spring-jack d to screw f, and thence through spring h and connecting-piece h of that springjack to Wire d, and thence to connectingpiecef of spring-jack d, and thence through screw j', spring l1., and connecting-piece h of that spring-jack to wire d", which Wire is connected directly to line No. 4, and through conmeeting-pieces la' k to test-bolts la 7c of spring- `jacks d d. The circuit then passes along the line No. 4 to the station outfit z, and through that outfit, as shown in Fig. ld. If there were more than two switch-boards, each having a spring-jack for the line, the circuit would be from one spring-jack to another in the manner The battery IOO l'IO

IZO

assess similar to that shown, so that all the contactsprings would be in the circuit, and the circuit, after passing through the contact-spring 7L of the last springjack, would be connected to all the pieces 7tof its series and to line. Line No. 2 could be traced in the same way, except that alter passing through its annun` ciator it is first connected through the springjackof its switch on switch-board A', where its calls are to be attended to. Every other line of the system would in like manner be connected to its series ot' switches and ot' testbolts and to ground and to its station outfit.

It will be seen from the description ot' the apparatus and the connections, as shown, that when there is no plug in any switch ofthe series of a line the circuit of the line through the boards and its annunciator to ground is unbroken, and when there is a plug in any switch of the series the circuit ot' the line to ground through the anuunciator is broken and the line is in electric connection with the cord which belongs to the plug.

It is evident that when a plug is inserted into the switch ot' any liuc at any board and its corresponding plug electrically connected with it is inserted into the switch of another line the two lines are disconnected from their annunciators and the ground at the central office and are connected to each other.

It is also evident that all the pieces It' of a series of switches belonging to a line are in conneetion with the line,whether the line is in use or not at any board.

Fig. 3 represents a central-ottico system ot connecting-cords with plugs, keys, switches, annunciators, telephone, battery, and circuits for answering, calling, testing, and clearing out subscribers7 lines. It represents the operators telcphone as connected with the ground on one and with the keys, switches, &c.,on the other side to the connecting-cords. It represents two pairs ot' cords with their keys, switches, and aununciators, and with one telephone and one signal battery or generator, the whole being intended as the outlit ol" oiie operator at one board ol' the central oi'lice. Other pairs ot' cords with their keys, tc., could in like manner be connected to the operators telephone and signal-battery, giving to each operator as many pairs ot' cords, Snc., as she might require in order to make the connections called ior by the subscribers assigned to her.

in Fig. l, O and G' represent two systems of cords, 5cc., with telephones and batteries for two operators-one at each board. Only one pair of cords is shown in each of these two systems.

i; and n in Figs. l and it are clearing-out annunciators.

p and p are three-point lever-swilches i jj heilig thecontact-bolts on which the levers can be placed at the will ot' the operators.

q q are spring keys for calling.

Ii' i" are spring-keys l'or listening l'or the erder and for clearingout purposes.

u a are the calling-batteries or generators.

D D2 and Dl1 Dl2 represent two pairs of 75 cords with their plugs. rlhe right-hand cords, or the ones marked DZ Dl2 are to be used to make connections with the springjacks of the calling subscribers. The cords marked D Dl1 are to be used to make connections with the spring-jacks ot' the subscribers who are to be called. Thecircuitsaresubstantially asshown. These systems may be called the operators systems of cords.

The operation of the complete telephone apparatus and system described above is as follows: \Vhen a calliug-annunciator at a board indicates a call, the operator places one of her plugs, which are intended to be used for calling subscribers lilies, into the springjack of the line on which the call is indicated, and pressing on the listening-key corresponding to that plug finds out who is wanted by the person who has called. She then takes the other plug ot' the pair she`is using and places it on the test-bolt ofthe line wanted,at the saine time holding her telephone to her ear. It, now, the station outfit of the subscriber whose line is being` tested is in use, or, in other words, if the telephone at his station is ott' from its switch, the operator hears a click or sound in her telephone, caused by the battery-current which is then going to line from the station-battery,shewill hear as many clicks as she makes and breaks the current in testing. She knows by the click that the subscribers outiit is already in use, and notities the calling subscriber to that effect and removes the plug from his spring-jack. It, on the other hand, the station outiit of the subscriber who is wanted is not in ilse, or, in other words, itthe telephone is on the hook, the operator will hear no click, and consequently knows that the station outtit is notin use. She then inserts the plug in the switch of the line, and, removing the lever of the switch correspondingl to the cords sheisusing from its bolt/i, presses on the keyqeorresponding to the cords, and thereby calls the subscriber wanted. She then moves the levcrp tothe boltj, and the two lines are connected together for conversation. Fig. l shows lines No. l and No. 2 connected together for conversation on board A. Figs. l and l" show the station outlits ot' these lines with their telephones oft' from their switches. ly pressing on i" the operator may listen to the conversation going 011 in the circuit of the two lines thus connected. 3y pressing on q the signaling-current will be sent to both lines, and on c she may receive the clearing-out signal to disconnect. On switch-board A, Fig. 1, the

cord Dt ot' system t) is connected with the spring-jack ot' line No. 3, and the operator IIO may, on pressing on key r, converse with the subscriber at station outfit Y. The telephone at Y is off from its switch for conversation. Now, if the operator places the plug D on the test-.bolt at a or b', she finds that the outfits of lines Nos. 1 and 2 are in use, and she proceeds no further in making connection with those lines. If she places the plug on the test-bolt at d, she will nd that the station outfit of line No. 4 is not in use, and she may then connect to that line and call the station and complete the connection in the mannerindicated above.

It will thus be seen that in this system, constructed and operated as described above, any

two lines centering at any office can be readily connected and disconnected at any board of the office and that any operator may readily test to.determine whether any line is in use or not.

I do not limit myself to the form of centraloffice switchboard which I have shown. My system of testing may be applied to any form of switch-boards suitable for telephone-exchanges, the only additional requirement being to provide a series of test-bolts-one bolt for each line on each board-the bolts of a se ries being connected with each other and with the line in such a way that they will always be connected with the line in whatever way it maybe switched.

I do not limit myself to the gravity formof telephone-switch in the station outfits. Any known forms of telephone-switches might be used wit-h proper' arrangement of parts and connections. f

In the modifications of subscribers station apparatus shown in Figs. Ie and lf the same parts are indicated by the saine numbers, as in Figs. l", l, l, and ld.

9 in Fig. 1C indicates a resistancecoil of suitable resistance, and l0 in Fig. 1f indicates an eXtra battery. The circuits in the two gures are substantially as shown, the solid lines being for the main line and the broken lines for the local circuits.

It will be seen that in the station apparatus shown in Figs. l, l, 1., ld, and lc electric current from the transmitter-battery will go to line when the subscriberstelephone-switch is in position for the telephone to be used, and none will go to line when it is not in that position,and that in the station apparatus shown in Fig. lfan extra battery is used,which sends a current to line when the telephone is being used, and only then in the combinations which I shall `hereinafter claim.

I donot wish to limit myself to anyparticular apparatus for sending currents to line.

rlhe batterycurrent sent to line when the line is in use for conversation should be sufficiently strong to be indicated by the testreceivingapparatus used at the central office.

It should, however, not be strong enough to operate the clearingout annunciator, if one is used. I have found by experience that with the apparatus generally in use in telephoneexchanges,when connected and used as shown in the drawings, the current is of the right strength to obtain these results. I prefer to use a telephone as the test-receiving instrument, as it is delicate enough to indicate a current of the strength mentioned above and can be conveniently used for this purpose and at the same time for the other operations of the attendant. A galvanoineter or other suitablev test-receiving instrumentmight, however, be used.

It is preferable that the batteries of the station outfits be so connected that they send the same polarities to line when Y their telephones are in use.

It will be seen that when the batteries are thus connected, and two lines are connected together for conversation with a clearing-out annunciator in their circuit, the batteries of the two lines will act in opposite directionson the clearing-out-annunciator magnet, andthe effective current acting on the magnet will be merely that due to the difference, if any, between the strength ofthe tivo batteries. Their eEfect, however, on a test-receiving instrument grounded on one side and connected on its other side to the circuit of the two lines will be that of two batteries acting together in multiple circuit, one in each line. Should, however, the batteries in the subscribers station apparatus of two lines connected together for conversation be connected into their circuitin such a manner that the currents from the two batteries pass in the saine direction, their effect on the test-receiving instrument would be that of two batteries sending currents of opposite direction through it, and should the batteries send equal strength of current through it no test-signal would be received, even when the lines were in use. To prevent this occurrence, I connect all the batteries, so that they will all send the same polarities of current to their lines.

I have shown closed-circuit lines grounded at the subscribers stations. If desired, any of the lines might be continued back to the office and there grounded.

My system of testing is applicable to opencircuit as well as to closed-circuit systems of exchanges. If the wires are normally open at the central office, the testbolt and the switch of a wire on each board may be one and the same, and may be a metallic socket adapted to receive the switch-plug.

Fig. 4 shows two multiple switch-boards for open-circuit lines with the metal sockets mentioned above, adapted both to receive the switch-plug and to perform the office of a test-v bolt for its line. ms ms in this figure represent these metallic sockets.

I claim as myinvention and desire to secure by Letters Patentl. In a telephonesubscribe1"s station outfit, the combination of a batterytransmitter,a battery, and a switch, said switch having a pair of contact-points which are closed when the switch is in position for the telephone to be used, and not otherwise, the transmitter being TOC IIO

in the circuit ofthe line and being shunted by a branch or derived circuit, in which are said battery and said pair of contact-points, substantially as set fort-h.

2. In a telephone-subscribers station outfit, the combination of a resistance, (of whatever kind,) a battery, and a switch, said switch having a pair of contact-points which are closed when the switch is in position for the telephone to be used, and not otherwise, the resistance being in the circuit of the line, and being shunted by a branch or derived circuit in which are said battery and said pair of contact-points, substantially as set forth.

3. In atelephone-subseribers station outfit, a battery-transmitter and the primary of its induction-coil in the circuit ofthe line,a switch having a pair of contact-points, and a battery, said battery and said pair of contact-points beingin abraneh or derived circuit which shunts said transmitter and primary of its inductioncoil,and said pair ofcontact-points being closed when the switch is in position for the telephone to be used, and not otherwise, substantially as set forth.

4:. In a telephone-exchange system, a telephone-line grounded at its outer end, a battery-transmitter with the primary of its induction-coil, a battery, and a switch at the subscriber-s station, said switch having apair of contact-points which are closed when the switch is in position for the telephone to be used, and not otherwise, said transmitter-,with its induction-coil, being in the circuit of the lines, and said battery and said pair of contact-points being in a branch or derived circuit which shunts said transmitter with its primary of the inductioncoil, in combination with a test-receiving instrument at the central office grounded on one side, and a switchtesting plug or device connected to said instrument on its other side, whereby an operator may at will counectit to the circuit of said. line, substantially as set forth.

5. In a telephone-exchange system, a telephone-line grounded at its outer end, a resist` ance, (of whatever kind,) a battery, and a switch at the subscribers station, said resistance being in the circuit of the line, said switch having a pair of contact-points which are closed when the switch is in position for the telephone to be used, and not otherwise, and said battery and said pair ot' contactpoints being ina branch or derived circuit which shunts said resistance, in combination with a test-receiving instrument grounded on one side, and a switch-testing plug or device connected to said instrument on its other side, whereby au operator may at will connect it to the circuit of said line, substantially as set forth.

6. In a telephoneexchangesystem, the combination of a telephone-line grounded at its outer end, two or more switch-boards, at either of which said line may be switched for conversation, and test-receivinginstruments, one at each board, each instrument being grounded on one side and connected on its other side to a switch-testing plug or device to connect it for testing with the circuit of the line, with a resistance, (of whatever kind,) a battery, and a switch at the subscribers station, said resistance being in the circuit of the line, said switch having a pair of contact-points which are closed when the switch is in position for the telephone to be used, and not otherwise, said battery and said pair of contact-points being in a branch or derived circuit which shunts said resistance, substantially as set forth.

7. In a telephone-exchange system,two telephone-lines grounded at their outer ends and connected together at the exchange-office for conversation, a battery, and a switch at the subscribers station of each line, each switch sending a current to line from its battery when the switch is in position for the telephone to be used, and not otherwise, and said batteries being so connected that their currents go in opposite directions through the circuit, in combination with a test-receiving instrument at the central office grounded on one side, and a switch-testing plug or device connected to the other side of said instrument, whereby an operator may at will connect it to the circuit of either line, substantially as set forth.

8. In a telephone-exchange system, two or more switch boards, at either of which the same lines may be switched for conversation, two lines temporarily connected together at one of said boards, a battery, and a switch at the subscriber-s station of each line, each switch sending a current to line from its battery when the switch is in position for the telephone to be used, and not otherwise, and said batteries being connected so that their currents go in opposite directions through the circuit, in combination with test-receiving instru ments, one at cach board, each instrument being grounded on oneside and connected on its other side to a switeh-testingplug or device, whereby an operator may at will connect it to the circuit of either line, substantially as set forth.

9. In a telephone-exchange system, two telephone-lines grounded at their outer ends and connected together at the central ollice for c'onversation, a clearing-out annunciator in the circuit of said lines at the central office, a battery, and a switch at the subscriber-s station of each line, each switch sending a current to line from its battery when the switch is in position for the telephone to be used, and not otherwise, and said batteries being so connected that their currents go in opposite directions through the circuit, in combination with a test-receiving instrumentat the central office grounded on one side, and aswitch-testing plug or device connected to the other side of said instrument, whereby an operator may at will connect it to the circuit of either line, substantially as set forth.

10. In a telephone-exchange system, a pair of central-office cords with plugs adapted for IOO IOS

use with `the line-switches, in combination With an operators telephone and a switch, r said cords being normally, or when not in use for conversation between two subscribers, dis- 5 connected from each other, and one of them vgrounded through the operators telephone,y

and said switch having contactpoints to disconnect said cord from its ground-connection through the telephone, and at the same time 1o connect it with the other cord for conversation.

1l. In a telephone-exchange system, a pair of central-ofce cords with plugs adapted for use With line-switches, in combination with I5 au operators telephone, a switch, and a key,

- it with the other cord for conversation.

MILO G. KELLGGG. `Witnesses:

CALVIN DE WOLF, MILTON HEAD. 

